Protection against electrostatic discharges and filtering

ABSTRACT

An electronic component includes first and second separate semiconductor regions. A third semiconductor region is arranged under and between the first and second semiconductor regions. The first and third semiconductor regions define electrodes of a first diode. The second and third semiconductor regions define electrodes of a second diode. The first diode is an avalanche diode.

PRIORITY CLAIM

This application claims the priority benefit of French Application forPatent No. 1852593, filed on Mar. 26, 2018, the content of which ishereby incorporated by reference in its entirety to the maximum extentallowable by law.

TECHNICAL FIELD

The present disclosure generally relates to electronic circuits, andmore particularly to a device for protection against electrostaticdischarges.

BACKGROUND

Some electronic circuits, such as integrated circuits, have to beprotected against electrostatic discharges. Such electrostaticdischarges risk reaching the circuit terminals, and are capable ofdamaging the circuit.

It is further desired to protect electronic circuits againstelectromagnetic disturbances which might reach those electronic circuitsand affect their operation, or even damage them.

SUMMARY

A device for protection against electrostatic discharges and forfiltering electromagnetic disturbances is thus provided which overcomingall or part of the disadvantages of known protection and/or filteringdevices.

In an embodiment, an electronic component includes first and secondseparate semiconductor regions and a third semiconductor region arrangedunder and between the first and second regions, the first and thirdregions defining electrodes of a first diode, the second and thirdregions defining electrodes of a second diode, and the first diode beingan avalanche diode.

According to an embodiment, the third region has a lower doping levelthan the first and second regions.

According to an embodiment, the third region is located on anelectrically-insulating layer.

According to an embodiment, the electrically insulating layer covers asupport having an electric resistivity greater than 1,500 Ωcm.

According to an embodiment, the support is a semiconductor wafer.

According to an embodiment, a third diode may be connected in parallelwith the first and second diodes.

According to an embodiment, the third diode includes first and secondseparate semiconductor areas and a third semiconductor area locatedunder and between the first and second areas, the first and second areasdefining electrodes of the third diode, and the first and second areasbeing more heavily doped than the third area.

According to an embodiment, the component includes, under the firstregion, an additional region of the same conductivity type as the thirdregion and more heavily doped than the third region.

According to an embodiment, a fourth region located above the thirdregion defines an electrode of a Schockley diode, another electrode ofwhich is defined by the second region.

According to an embodiment, the fourth region is not located above theadditional region.

According to an embodiment, the fourth region is located in an upperportion of the first region.

According to an embodiment, the fourth region is located in an upperportion of a fifth region of the same type of conductivity as the firstand second regions, the third region extending below and between thesecond and fifth regions.

According to an embodiment, the component has a first contact toppingthe first region and a second contact connected to the first contact andlocated astride the fourth region and the first region or the fifthregion.

An embodiment provides a device for protection against electrostaticdischarges includes at least one component such as above.

An embodiment provides a circuit including the component above.

According to an embodiment, the circuit includes an inductive element inseries with the component.

According to an embodiment, the inductive element is arranged on theelectrically-insulating layer.

According to an embodiment, no semiconductor portion is located betweenthe electrically-insulating layer and the inductive element.

According to an embodiment, the inductive element is located on aportion of a semiconductor layer arranged on the electrically-insulatinglayer.

An embodiment provides a device for common-mode filtering and forprotection against electrostatic discharges, including first and secondcircuits above, the inductive elements of the first and second circuitsbeing mutually magnetically coupled.

According to an embodiment, the inductive element of the first circuitincludes first conductive tracks, and the inductive element of thesecond circuit includes second conductive tracks stacked to the firstconductive tracks.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages will be discussed indetail in the following non-limiting description of specific embodimentsin connection with the accompanying drawings, wherein:

FIG. 1 schematically illustrates a protection and filtering device,comprising two components for protection against electrostaticdischarges;

FIG. 2 is a simplified cross-section view of the device of FIG. 1;

FIG. 3 is a simplified cross-section view illustrating a portion of anembodiment of a filtering device ensuring protection againstelectrostatic discharges;

FIG. 4 is a simplified cross-section view illustrating a portion of analternative embodiment of the device of FIG. 3; and

FIG. 5 is a simplified cross-section view illustrating a portion ofanother alternative embodiment of the device of FIG. 3.

DETAILED DESCRIPTION

The same elements have been designated with the same reference numeralsin the various drawings and, further, the various drawings are not toscale. For clarity, only those steps and elements which are useful tothe understanding of the described embodiments have been shown and aredetailed. In particular, the electronic circuits to be protected areneither shown, nor detailed, the described embodiments being compatiblewith current electronic circuits utilizing protection againstelectrostatic discharges.

In the following description, when reference is made to terms qualifyingabsolute positions, such as terms “front”, “rear”, “top”, “bottom”,“left”, “right”, etc., or relative positions, such as terms “above”,“under”, “upper”, “lower”, etc., or to terms qualifying directions, suchas terms “horizontal”, “vertical”, etc., it is referred to theorientation of the concerned element in the cross-section views, itbeing understood that, in practice, the described devices may beoriented differently. Unless otherwise specified, expressions“approximately”, “substantially”, and “in the order of” mean to within10%, preferably to within 5%.

In the present description, the term “connected” designates a directelectric connection between two elements, while the term “coupled”, whenit relates to an electric connection, designates an electric connectionbetween two elements which may be direct or via one or a plurality ofpassive or active components, such as resistors, capacitors,inductances, diodes, transistors, etc.

FIG. 1 schematically illustrates a device 100 for protection againstelectrostatic discharges and for filtering of electromagneticdisturbances.

Device 100 comprises two input terminals A0 and B0 and two outputterminals A1 and B1. Terminals A1 and B1 are connected to an electroniccircuit to be protected.

Device 100 comprises two inductive elements 200A and 200B. Inductiveelement 200A couples terminal A1 to terminal A0. Inductive element 200Bcouples terminal B1 to terminal B0. Inductive elements 200A and 200B aremagnetically coupled and thus form a transformer. The transformationratio of the transformer is preferably on the order of one, preferablyequal to 1.

In operation, inductive elements 200A and 200B block common-modeelectromagnetic disturbances. Inductive elements 200A and 200B enable toconduct toward the electronic circuit signals defined by differentialmodes between terminals A0 and B0. Device 100 plays the role of acommon-mode filter (CMF).

Device 100 further comprises two components 300A and 300B for protectionagainst electrostatic discharges. Components 300A and 300B respectivelycouple terminals A0 and B0 to a node of application of a referencepotential, for example, a ground GND.

Each of components 300A and 300B comprises a node 304 and a node 302.Node 304 is connected to the considered terminal A0 or B0. Node 302 is,for example, connected to ground. In each protection component, a diode320 has its cathode coupled to node 304 and its anode coupled to node302. In parallel with diode 320, a diode 340 and a diode 360 in seriescouple node 304 to node 302. Diodes 340 and 360 have their cathodesinterconnected, and their anodes respectively connected to nodes 304 and302. Diode 360 is an avalanche diode, for example, a Zener diode, or a“Transil”-type (transient-voltage-suppression) diode. Such a diode isdesigned to have an avalanche voltage, for example, of a value smallerthan 30 V, preferably smaller than 10 V.

Device 100 is provided so that in normal operation, the potentials ofterminals A0 and B0 are positive. In the occurrence of an electrostaticdischarge tending to increase the potential of terminal A0 or B0, thedischarge is drained off to ground by diodes 340 and 360. In the case ofan electrostatic discharge tending to make the potential of terminal A0or B0 negative, the discharge is drained off to ground by diode 320.

FIG. 2 is a simplified cross-section view of the device of FIG. 1.Components 300A and 300B are formed inside and on top of a substrate400, for example, a wafer of a semiconductor such as silicon. Inductiveelements 200A and 200B each comprise a conductive track arranged ininsulator layers 410, not shown in detail, covering substrate 400. Thetrack of each inductive element, for example, runs several times, fourturns being shown as an example. The inductive elements 200A, 200B maybe disposed around the location of the components 300A and 300B, orpreferably outside the location of the components 300A and 300B. Thetracks of the inductive elements are stacked, which provides themagnetic coupling between these elements. The various connections, notshown, between inductive elements 200A, 200B and components 300A, 300Bare typically formed by conductive tracks in insulator layers 410.

FIG. 3 is a simplified cross-section view illustrating a portion of anembodiment of a device 500 for protection against electrostaticdischarges of the type of device 100 of FIGS. 1 and 2. FIG. 3corresponds to an enlargement of the left-hand portion of FIG. 2. Inparticular, device 500 comprises inductive elements 200A and 200B andcomponents 300A and 300B of the above-described type. Only component300A is shown and detailed hereafter, since component 300B may besimilar to component 300A, for example, symmetrical.

A P-type doped semiconductor region 342 defines the anode of diode 340.A P-type doped semiconductor region 362 defines the anode of avalanchediode 360. A semiconductor region 510, for example, of type N, common tothe two diodes 340 and 360, defines the interconnected cathodes ofdiodes 340 and 360.

Regions 342 and 362 are separate and located in the upper portion ofsemiconductor region 510. Regions 342 and 362 are thus located on theside of a same surface of semiconductor region 510, a portion ofsemiconductor region 510 extending between regions 342 and 362.Avalanche diode 360 may comprise a region 364 more heavily N-type dopedthan region 510, for example, located under region 362. Regions 342 and362 are, for example, topped with respective contacts 346 and 366connecting regions 342 and 362 respectively to nodes 304 and 302.

Such a layout of the semiconductor regions defining diode 340 andavalanche diode 360 enables limiting of the stray capacitance of theseries coupling, in particular when region 510 is depleted in normaloperation. Such a stray capacitance may be low, for example, smallerthan 0.3 pF, even for large surface areas of regions 342 and 362, forexample, greater than 15,000 μm². Thereby, device 500 enables couplingoutput terminals A1 and B1 to a signal having a particularly highfrequency, for example, greater than 3 GHz. Further, decreasing thestray capacitance enables increasing of the rapidity of the deviceduring the occurrence of an electrostatic discharge. Further, the deviceenables to drain off to ground currents of high intensities, forexample, greater than 10 A, which enables reinforcement of theprotection level during the occurrence of an electrostatic discharge.

As an example, semiconductor region 510 has a low N type doping level,for example, so that its electric resistivity at 25° C. is greater than100 Ω·cm.

Semiconductor region 510 is, for example, a portion of a semiconductorlayer 420 on top of and in contact with an insulating layer 430.Insulating layer 430 covers and is, for example, in contact with asupport 440. Region 510 is delimited by insulating trenches 450 filledwith an electric insulator, for example, silicon oxide. The device canthen be obtained from a structure of semiconductor-on-insulator type,for example, of silicon-on-insulator or SOI type comprising support 440,insulating layer 430, for example, made of silicon oxide, and layer 420.As an example, the thickness of layer 420 is in the range from 1 to 15μm, preferably in the order of 10 μm. The thickness of layer 430 is, forexample, in the range from 0.2 μm to 2 μm.

Preferably, support 440 is electrically insulating, for example, made ofsilicon oxide or of sapphire, or of a semiconductor of high resistivity,for example, greater than 1,500 Ω·cm.

Region 510 may then be depleted in operation across its entire thicknessunder the region 342, which limits the stray capacitance of the seriescoupling of diodes 340 and 360. Further, the provision of anelectrically insulating or high-resistivity support enables to limit thestray capacitances between the series coupling of the diodes and support440. This enables the device to couple signals up to particularly highfrequencies, and ensures the rapidity of the device during theoccurrence of an electrostatic discharge.

It should further be noted that problems of exodiffusion of dopant atomswhich would risk occurring from the support if the support was made of adoped semiconductor which would be less resistive than a semiconductorof high resistivity are avoided.

An N-type doped region 368 may be provided in the upper portion ofregion 362. Region 368 is, for example, located outside of the portionof region 362 covered with contact 366. Region 368 is, for example,located in a portion of region 362 located on the side of region 342.Region 368 is, for example, not located above region 364. Region 368 is,for example, more heavily doped than region 362. A contact 370 coversboth a portion of region 368 and a portion of region 362 andelectrically couples the two regions to node 302.

A Schockley diode has thus been defined by regions 342 (P), 510 (N), 362(P), and 368 (N). During the occurrence of an electrostatic discharge,the Schockley diode starts conducting, which enables providing a higherprotection level than in the absence of doped region 368. Further, thisenables draining an electrostatic discharge to ground without thisdischarge being absorbed by the association in series of diodes 340 and360. The risk of these diodes being damaged by the discharge is thusavoided.

In the right-hand portion of FIG. 3, diode 320 of device 300 comprises,as an example, an N-type region, or area 322 of low doping level, forexample, of same resistivity as region 510. Separate N-type regions orareas 324 and P-type regions 326 more heavily doped than region 322 arelocated in the upper portion of region 322. Regions 324 and 326 are, forexample, topped with respective contacts 328 and 330 connecting regions324 and 326 respectively to nodes 304 and 302.

As an example, for a structure of semiconductor-on-insulator typecomprising layers 430 and 420 on support 440, regions 510 and 322 arepreferably portions of semiconductor layer 420.

The layout of the regions defining diode 320 enables, due to the factthat region 322 may be depleted in normal operation, limitation of thestray capacitance of diode 320. Further, the provision of anelectrically-insulating or high-resistivity support 440 enables limitingstray capacitances between the diode and the support.

In the left-hand portion of FIG. 3, stacked inductive elements 200A and200B are as an example arranged on a portion 520 of semiconductor layer420. Portion 520 is located on insulating layer 430 and, for example,has a low N-type doping level. Portion 520 is, for example, of sameresistivity as region 510 and originates from the same semiconductorlayer 420 of a semiconductor-on-insulator structure.

The provision, under the stacked inductive elements, of region 520 ofhigh electric resistivity, of insulator 430, and ofelectrically-conductive or high-resistivity support 440, enableslimiting the stray capacitance between the inductive elements and thesupport. The device 500 couples signals in differential mode and blockscommon-mode electromagnetic disturbances up to high frequencies, forexample, greater than 3 GHz.

FIG. 4 is a simplified cross-section view illustrating a portion of analternative embodiment of the device of FIG. 3. In the variation of FIG.4, portion 520 of semiconductor layer 420 has been removed. A step ofetching of this portion may, for example, be provided. This leads to anabsence of a semiconductor portion between the inductive elements 200Aand 200B and the insulating layer 430 of the SOI structure. Theinductive elements are located on electric insulators only, or onelectric insulators and the high resistivity support 440 only. As aresult, the device 500 couples signals in differential mode and blockscommon-mode electromagnetic disturbances up to particularly highfrequencies.

FIG. 5 is a simplified cross-section view illustrating anotherembodiment of the device of FIG. 3. The device of FIG. 5 differs fromthe device of FIG. 3 in that the region 510 further extends under andbetween a P-type doped region 372 and the P-type doped region 342 of thediode 340, the region 368 is replaced by an N-doped region 374 locatedin an upper portion of the region 372, preferably on the side closest tothe region 342, and the contact 370 is replaced by a contact 376,covering both a portion of the region 372 and a portion of the region374, and electrically coupling both regions 372 and 376 to the node 302.

As an example, the N-type region 364 is located under and around theregion 362.

The regions 342 (P), 510 (N), 372 (P) and 374 (N) thus define aSchockley diode that replaces and plays the role of the Schockley diodeof the device of FIG. 3. The protection level provided by the device ofFIG. 5 is higher than the protection level provided by the device ofFIG. 3.

Specific embodiments have been described. Various alterations,modifications, and improvements will occur to those skilled in the art.In particular, a single protection component of the type of component300A coupling a terminal to ground, and providing protection againstelectrostatic discharges reaching this terminal may be provided. Afiltering inductive element similar to element 200A may then beprovided. Further, diode 320 may be replaced with any diode adapted tothe protection against electrostatic discharges.

Further, the doping types may be exchanged in components 300A and/or300B. The sign of the voltages and the connection direction ofcomponents 300A and/or 300B between terminals A0 and/or B0 and theground may then be modified.

Various embodiments with various variations have been describedhereabove. It should be noted that those skilled in the art may combinevarious elements of these various embodiments and variations withoutshowing any inventive step.

Finally, the practical implementation of the described embodiments iswithin the abilities of those skilled in the art based on the functionalindications given hereabove.

1. An electronic component, comprising: first and second semiconductorregions; and a third semiconductor region arranged under the first andsecond semiconductor regions and further extending between the first andsecond semiconductor regions to separate the first semiconductor regionfrom the second semiconductor region; wherein the first and thirdsemiconductor regions define electrodes of a first diode, the firstdiode being an avalanche diode; and wherein the second and thirdsemiconductor regions define electrodes of a second diode.
 2. Theelectronic component of claim 1, wherein the third semiconductor regionhas a lower doping level than the first and second semiconductorregions.
 3. The electronic component of claim 1, wherein the thirdsemiconductor region is located on an electrically insulating layer. 4.The electronic component of claim 3, wherein the electrically insulatinglayer covers a support having an electric resistivity greater than 1,500Ω/cm.
 5. The electronic component of claim 4, wherein the support is asemiconductor wafer.
 6. The electronic component of claim 1, furthercomprising a third diode connected in parallel with the first and seconddiodes.
 7. The electronic component of claim 6, wherein the third diodecomprises: first and second semiconductor areas; and a thirdsemiconductor area located under the first and second semiconductorareas and further extending between the first and second semiconductorareas to separate the first semiconductor area from the secondsemiconductor area; wherein the first and second semiconductor areasdefine electrodes of the third diode; and wherein the first and secondsemiconductor areas are more heavily doped than the third semiconductorarea.
 8. The electronic component of claim 1, further comprising, underthe first semiconductor region, an additional semiconductor region of asame conductivity type as the third semiconductor region and moreheavily doped than the third semiconductor region.
 9. The electroniccomponent of claim 1, further including a fourth semiconductor regionthat is located above the third semiconductor region and which definesan electrode of a Schockley diode, and wherein another electrode of theSchockley diode is defined by the second semiconductor region.
 10. Theelectronic component of claim 9, wherein the fourth semiconductor regionis not located above the additional semiconductor region.
 11. Theelectronic component of claim 9, wherein the fourth semiconductor regionis located in an upper portion of the first semiconductor region. 12.The electronic component of claim 9, further including a fifthsemiconductor region of a same type of conductivity as the first andsecond semiconductor regions, wherein the third semiconductor regionextends below and between the second and fifth semiconductor regions toseparate the second semiconductor region from the fifth semiconductorregion, and wherein the fourth semiconductor region is located in anupper portion of the fifth semiconductor region.
 13. The electroniccomponent of claim 12, further comprising: a first contact on the firstsemiconductor region; and a second contact connected to the firstcontact and located astride the fourth semiconductor region and thefirst semiconductor region or the fifth semiconductor region.
 14. Theelectronic component of claim 1, further comprising an inductive elementcoupled to an electrode of the second diode.
 15. The electroniccomponent of claim 14, wherein the third semiconductor region is locatedon an electrically insulating layer and wherein the inductive element isarranged above the electrically insulating layer.
 16. The electroniccomponent of claim 15, wherein no semiconductor portion is locatedbetween the electrically insulating layer and the inductive element. 17.The electronic component of claim 15, wherein the inductive element islocated above a portion of a semiconductor layer arranged on theelectrically insulating layer.
 18. A device for protection againstelectrostatic discharges comprising at least one electronic componentaccording to claim
 1. 19. A circuit comprising an electronic componentaccording to claim
 1. 20. A device for common mode filtering andprotection against electrostatic discharges, the device comprising: afirst circuit comprising: a first electronic component comprising: firstand second semiconductor regions; and a third semiconductor regionarranged under the first and second semiconductor regions and furtherextending between the first and second semiconductor regions to separatethe first semiconductor region from the second semiconductor region;wherein the first and third semiconductor regions define electrodes of afirst diode, the first diode being an avalanche diode; and wherein thesecond and third semiconductor regions define electrodes of a seconddiode; and a first inductive element coupled to an electrode of thesecond diode; and a second circuit comprising: a second electroniccomponent comprising: fourth and fifth semiconductor regions; and asixth semiconductor region arranged under the fourth and fifthsemiconductor regions and further extending between the fourth and fifthsemiconductor regions to separate the fourth semiconductor region fromthe fifth semiconductor region; wherein the fourth and sixthsemiconductor regions define electrodes of a third diode, the thirddiode being an avalanche diode; and wherein the fifth and sixthsemiconductor regions define electrodes of a fourth diode; and a secondinductive element coupled to an electrode of the fourth diode; whereinthe first and second inductive elements are mutually magneticallycoupled.
 21. The device of claim 20, wherein the first inductive elementof the first circuit comprises first conductive tracks, and the secondinductive element of the second circuit comprises second conductivetracks stacked on the first conductive tracks.